Non-isothermal differential thermal analysis in the study of the initial state of the thermal decomposition of polynitroaromatic compounds in the condensed state

The activation energies, E, of the decomposition of picramide and its N-methyl-,N-ethyl-,N-n-propyl- and N-n-butyl-derivatives are determined by means of non-isothermal DTA, in its simple form, as well as by the Piloyan method. A relationship is found between the E values of the above-mentioned compounds and the published values of the moments of inertia of the corresponding n-alkyl groups. Taking into account data published previously, which were obtained by application of the Piloyan method in the DTA of polynitroaromates, it is concluded that by suitable selection of DTA measurement conditions, it is possible to record the early part of the exothermal decomposition of the above-mentioned compounds were no autocatalytic influence exists. Attention is also paid to the thermostability of the polynitroaromates due to their contact with the construction materials employed in the course of thermolysis.     

Use of emanation thermal analysis and evolved gas analysis in thermal study of zinc(II) benzoate complex compounds

Volatile organic compounds (VOCs) are the main factors involved in pollution control and global warming in industrialized nations. Various treatment methods involving incineration, adsorption, etc., were employed to reduce VOCs concentration. Various absorbents, such as activated carbon, zeolite, silica gel or alumina, and so on were broadly used to adsorb VOCs in various industrial applications. Differential scanning calorimetry (DSC) was handled to analyze the thermal characteristics of absorbents. Typically, a scanning electron microscope (SEM) has been used to evaluate the structure variation of absorbents under high temperature situations. In view of pollution control and loss prevention, versatility and analysis of recycled adsorbents are necessary and useful for various industrial applications.     

High pressure DSC of phenolformaldehyde moulding compounds

The influence of pressure on the polycondensation reaction between novolac resin (N) present in commercially available moulding compounds and hexamethylenetetramine (HMTA) was studied up to 80 bars under air and in an inert atmosphere. For a low HMTA content (N/HMTA=98/2 mass ratio) high pressure enables the detection of two successive curing reactions. With increasing HMTA content the peak due to the first curing reaction becomes less pronounced at high pressure, while the enthalpy of the second increases. In an inert atmosphere both curing reactions are well observable even at ambient pressure and for lower HMTA content take place at lower temperatures, as expected. For the sample with N/HMTA=98/2 the curing reaction was followed using TG-MS.     

Application of thermal analysis to the study of several Spanish peats

Thermogravimetry and differential thermal analysis have been applied to the study of peats from the main Spanish basements.The results obtained show that the degree of transformation of the organic matter increases as the depth of the peat increases.The intensity of the weight loss corresponding to the first exothermic effect (directly related to the carbohydrate content of the sample, and inversely related to the content of humic compounds) is, in the case of the peats with a high degree of transformation, strongly influenced by the nature of their humic acids.On the other hand, the displacement of this exothermic effect towards lower temperatures is directly related to the ash content of the samples.

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Zusammenfassung Die thermogravimetrische Analyse und die Differentialthermoanalyse wurden zum Studium von Torfen aus den wichtigsten spanischen Lagerstätten eingesetzt.Die erhaltenen Ergebnisse zeigen, daß der Umwandlungsgrad der organischen Substanz mit zunehmender Tiefe des Torfes zunimmt.Die Intensität des dem ersten exothermen Effekt entsprechenden Gewichtsverlustes (welcher dem Kohlenhydratgehalt der Probe direkt und seinem Huminverbindungsgehalt umgekehrt proportional ist) wird im Falle von Torfen von hohem Umwandlungsgrad durch die Beschaffenheit ihrer Huminsäuren stark beeinflußt.Andererseits ist die Verschiebung dieses exothermen Effekts in Richtung der niedrigeren Temperaturen dem Aschegehalt der Proben direkt proportional.

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Application of thermal analysis to study smelting reduction kinetics

A thermal analysis study on the reduction of iron oxide rich slags under different conditions is presented in this paper. The effects of important process variables such as time, temperature, lime-silica ratio, FeO level in slag etc. are discussed. It is shown that the mechanism of reduction by externally added graphite is different from that by a carbon saturated bath although the activation energy values are similar.     

Application of thermal analysis in study of binary mixtures with metformin

Thermal analysis is an essential analytical tool in development of new formulations as well as to study the interaction between drugs and excipients. This work aims to investigate the possible interactions between metformin and excipients as microcrystalline cellulose (Microcel MC101®), starch sodium glycolate (Explosol®), sodium croscarmellose (Explosel®), PVP K30, magnesium stearate, starch and lactose, usually employed in pharmaceutical products. TG, DSC and DTA techniques were used for the thermal characterization to track if the thermal properties of the drug substance were modified in the mixture. Disregard of the starch and lactose systems, no changes in thermal behavior of mixtures were found. Thermogravimetric studies (TG) of metformin and its binary mixtures showed different thermal behavior.     

Application of thermal analysis to study the causes of disintegration in insulating systems

In the procduction of high-voltage insulating systems, disintegration and non-homogeneity occur in some cases and these factors can lead to the deterioration and even the breakdown such systems. In research into the causes of these phenomena DTA and TG were applied to study the course of hardening of the systems and to quantify the leaking substances. The results demonstrate the great value of thermal analysis in this field.     

Application of thermal analysis to the study of the kinetics of two-stage reactions

A method is suggested for studying the kinetic parameters of two-stage reactions from thermoanalytical experimental data. The method allows determination of the kinetic characteristics of the process on the basis of integral thermoanalytical data, without separation of the individual stages. Parallel, independent and successive reactions taking place under isothermal and non-isothermal conditions are considered.

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Zusammenfassung Eine Methode zur Untersuchung der kinetischen Parameter von Zweistufenreaktionen unter Verwendung experimenteller thermoanalytischer Daten wird vorgeschlagen. Die Methode ermöglicht, die kinetischen Kennwerte des Prozesses basierend auf integralen thermoanalytischen Werten ohne Trennung der individuellen Schritte zu bestimmen. Unter isothermen und nichtisothermen Bedingungen parallel, unabhängig voneinander und nacheinander verlaufende Reaktionen werden diskutiert.

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Application of inorganic compounds at the thermal processing of polyvinylchloride

A review of publications on the effect of various inorganic additives (metals oxides, hydroxides, chlorides and carbonates) on the process of dehydrochlorination and pyrolysis at the thermal processing of polyvinylchloride (PVC). A decrease in temperature of the PVC dehydrochlorination step is noted at processing in the presence of chromium, iron, cobalt, copper and molybdenum oxides. Aluminum, titanium, circonium, cerium and lead oxides do not change temperature of beginning of PVC destruction. No effect noted of the oxides at the second step of PVC destruction.     

FTIR analysis of bentonite in moulding sands

Bentonite is used in a wide range of applications. One of them is the foundry industry. The aim of this study was to investigate modification of moulding sands by dust which is generated during foundry process. Recycling of this dust is very important from ecological point of view. The samples of moulding sands were examined by Fourier Transform Infrared spectroscopy (FTIR). Analysis of the bands due to the Si–O stretching vibrations allows to reveal the changes of active bentonite and silica sand, i.e. the main components of the moulding sands. FTIR results are compared with technological properties of the materials studied. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods have been used as the complementary measurement.     

Application of thermal analysis to the study of lipidic prodrug incorporation into nanocarriers

Anti HIV molecules as numerous drugs cannot efficiently penetrate into the brain. Prodrug synthesis and encapsulation into pegylated nanocarriers have been proposed as an approach for brain delivery. Pegylated polymeric nanoparticles and liposomes were chosen to incorporate glycerolipidic prodrugs of didanosine. Differential scanning calorimetry experiments were performed on mixtures of prodrugs and lipids or polymer in order to study their interaction. The optimal incorporation ratios were determined for each prodrug and compared for both types of nanocarriers. All these results would be used to prepare optimised formulations of didanosine prodrugs loaded into pegylated nanocarriers for brain drug delivery.     

Thermogravimetry under quasi-equilibrium conditions utilized in the study of the thermal dissociation of compounds

Study of the kinetics of multi-stage thermal dissociation reactions is a difficult task. Utilization of thermogravimetry under quasi-equilibrium conditions allows determination of intermediate phases, and if necessary their separation, in order to permit study of the kinetic stability separately. Parallel utilization of thermogravimetry under linear heating and quasi-equilibrium conditions allows detection of the existence of intermediate metastable phases.

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Zusammenfassung Die Untersuchung der Kinetik von über viele Schritte verlaufenden thermischen Dissoziationsreaktionen ist ein schwieriges Unterfangen. Mittels Thermogravimetrie unter Quasi-Gleichgewichtsbedingungen können intermediÄre Phasen bestimmt und — falls notwendig — abgetrennt werden, um die kinetische StabilitÄt gesondert zu bestimmen. Parallele Anwendung der linearen nicht-isothermen und der quasi-isothermen Thermogravimetrie ermöglicht den Nachweis von metastabilen intermediÄren Phasen.

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Application of differential thermal analysis in mineralogy

In mineralogical research differential thermal analysis can be applied as either a single or a combined method for three purposes:

1. for the qualitative identification of minerals and the (semi-)quantitative determination of the components of rocks and soils,
2. for the characterization of crystal-physical and crystal-chemical properties, including the study of kinetics and the determination of thermodynamic data, phase and reaction equilibria,
3. for special petrogenetic investigations concerning the interrelation of mineralogical properties with the formation, decomposition or recrystallization of minerals.

The presented results were obtained under strongly standardized and reproducible conditions of analysis and by means of some methods recently developed by the author. They include the construction of key diagrams ofΔT versus peak temperatures to identify unknown minerals; the dependence of dehydration and decomposition peak temperatures on the partial pressure of gaseous reaction products (= PA curves); the determination of chemical and crystal-chemical parameters of minerals by using the dependence of dehydroxylation peak temperatures on solid solution (chlorites, smectites) or by using the interrelation between the peak temperatures of structural transformations and crystal-chemical substitutions (sulfides, carbonates, phosphates, silicates); the determination of the degree of disorder of minerals formed in sedimentary environments by using the dehydration or inversion peak temperature and peak shape dependence on the defect character of these crystal structures (clay minerals, quartz, cristobalite, hydroxides); the subdivision of mineral groups by using the interrelation of crystal chemistry and dehydration behaviour (zeolites, mixed-layer clay minerals); the characterization of ferromagnetic minerals by studying the Curie temperatures as a function of the chemical composition; the development of a DTA method to measure the degree of weathering of granitic rocks, etc. Data of 150 minerals are given.     

Application of thermal analysis to study the macroredox polymerization of styrene with hydroxy-terminated polybutadiene

Ceric ammonium nitrate-hydroxy-terminated polybutadiene macroredox initiator has been investigated for the polymerization of styrene in nitric acid medium at 35 °C. Water inhibited the polymerization of styrene using this macroredox system. The products obtained were crosslinked and insoluble in water and organic solvents. A probable mechanism for the copolymerization reaction has been inferred from differential scanning calorimetry. Kinetic parameters for thermal degradation have been calculated by thermogravimetry (TG).     

Application of thermal analysis to the study of anti-tuberculosis drug compatibility. Part 1

Worldwide Brazil is among one of the 22 countries with high rates of tuberculosis placing this disease as a priority for the Government Health Policies in this country. Studies with the main tuberculostatic drugs rifampicin, isoniazid, pyrazinamide, and ethambutol, aiming the development of fixed-dose combination formulations (FDCs) have been performed. The aim of this study was to evaluate the thermal behavior of these drugs by DSC, TG/DTG, and DTA in order to predict possible physical and chemical interactions between tuberculostatics. DSC and DTA curves suggested incompatibility and/or interactions among drug preparations resulting from new thermal events, as well as the disappearance and shift of the melting point of the drugs. TG/DTG curves of drug mixtures presented different profiles from those observed for the individually tested drugs, supporting the evidence of drug incompatibility and indicating that mixtures are less stable when compared to the drugs alone.     

Application of thermal analysis to study of phase composition changes in blast furnace sinters

Application of thermal analysis to determine a quantity portion of iron oxides in symmetric blast furnace sinters is presented. In the multicomponent sample, calcium ferrites and many silicate phases beside doped iron oxides phases were observed. The dependence of sinter phase composition from basicity and relation with physicochemical properties is defined.     

Application of oxine in the polarographic analysis of organometallic compounds

Summary A procedure for the microdetermination of Cd, Mg, Zn, Mn, and Co in organometallic compounds is presented. After closed-flask combustion, the metal-oxine complex is precipitated from an ammonia-ammonium chloride buffered medium of pH 10. At this pH value oxine gives a well-defined polarographic wave. The wave height of an excessive volume of oxine is measured before and after it has been used to precipitate a known weight of the organometallic compound. The method is simple and rapid; one determination consumes 25 minutes. The average % error amounts to ± 0.53.

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Zusammenfassung Ein Verfahren zur Mikrobestimmung von Cd, Mg, Zn, Mn und Co in metallorganischen Verbindungen wurde angegeben. Nach Verbrennung im verschlossenen Kolben wird das Metall als Oxinat aus einer mit Ammoniak-Ammoniumchlorid auf pH 10 gepufferten Lösung gefällt. Bei diesem pH gibt Oxin eine gut ausgeprägte polarographische Stufe. Deren Höhe für einen Oxinüberschuß vor und nach der Fällung einer bekannten Menge metall-organischer Probe wird gemessen. Die Methode ist einfach und rasch. Eine Bestimmung dauert 25 min. Der durchschnittliche Fehler beträgt ± 0,53%.

     

Use of emanation thermal analysis in the study of thermal behaviour of inorganic materials

Emanation thermal analysis [1, 2] (ETA) is based on the measurement of the inert gas release from samples previously labelled. The high detection sensitivity of radioactive nuclides used for the measurement makes it possible to use very low concentrations of the inert gases (10^–14 at %) so that no influence of the inert gases on the properties of the solids can be supposed.

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Zusammenfassung Emanations — Thermoanalyse [1, 2] (ETA) basiert auf der Messung von freigesetztem inerten Gas aus zufor markierten Proben. Die große Nachweisempfindlichkeit der bei der Messung verwendeten radioaktiven Nuklide ermöglicht die Anwendung sehr niedriger konzentrationen (10^–14 Atom%) für das inerte Gas. Somit kann angenommen werden, daß die Eigenscahften des Feststoffes durch das inerte Gas nicht beeinflußt werden.

     

Application of thermal analysis to the cement industry

Methods involving heat measurements have been applied in the cement industry for a long time. Differential thermal analysis (DTA) is used to explain the clinkering reactions, but it is a dynamic method which thus does not allow measurements and calculations of the thermal balance of the reactions to be made. In contrast, high temperature microcalorimetry may be used to measure the enthalpy of the clinkering reactions of industrial raw materials. Results obtained by using this technique allow us to determine the thermal profile of clinkering reactions in the kiln and to quantify the heat exchange in the solid material during its burning.Low temperature conduction microcalorimetry gives information on the hydration mechanism of the cement pastes. In this paper, we review the applications of thermal analysis in the cement industry paying special attention to new methods such as high temperature microcalorimetry.

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Zusammenfassung Seit langer Zeit werden in der Zementindustrie Verfahren mit Wärmemessung angewendet. Zur Erforschung der Verschlackungsreaktionen wird DTA verwendet, was jedoch ein dynamisches Verfahren ist und keine Messungen und Berechnungen bezüglich des thermischen Gleichgewichtes erlaubt. Im Gegensatz dazu kann Hochtemperatur-Mikrokalorimetrie zur Messung der Enthalpie von Verschlackungsreaktionen industrieller Rohstoffe dienen. Mit Hilfe der durch diese Methode erlangten Resultate kann das thermische Profil von Verschlackungsreaktionen im Kiln und der Wärmeaustausch im Festmaterial beim Brennen bestimmt werden.Niedertemperatur-Konduktions-Mikrokalorimetrie liefert Informationen über den Hydratationsmechanismus von Zementleim. Unter spezieller Beachtung neuer Methoden, wie z.B. der Hochtemperatur-Mikrokalorimetrie, wird in diesem Artikel ein Überblick über die Anwendungen der Thermoanalyse in der Zementindustrie gegeben.